Here you should provide the estimated total amount you expect to receive for working for your US employer that invited you to Sprintax Calculus.
Please note it’s absolutely OK to provide an estimated amount that you personally expect to receive.
Make sure to only provide the relevant annual amount for the year you’re completing your Calculus application for. You do not need to calculate any previous or future years, only the amount you will receive for the year you’re filling out the questionnaire for.